The finished circumferences are 18.75” (47.5 cm), 20.5” (52 cm), 22.25” (56.5 cm), and 24” (61 cm). Most people like their hats snug, so choose a finished hat size that is slightly smaller than your actual head.
You can make this hat with fingering weight yarn held double with lace weight silk mohair (180-230 yds of each), or a DK weight yarn (180-230 yds). I knit this sample in La Bien Aimee DK Merino, (100% Merino wool, 252 yds/230 m per 4 oz/115 g), in the colorway Nadia.
You'll need a set of small-circumference knitting needles (suggested needle sizes: US 8/5 mm and US 5/3.75 mm), one stitch marker, and a tapestry needle for weaving in ends.